The last time I used WSL (perhaps 6 months ago), its per-process overhead was awful. I don't recall the numbers, but I think it managed to start fewer than 10 processes per second. My memory suggests it was more like two processes per second, though I would recommend re-testing before trusting that.
On 1803 and 1903 it's 3 to 4 times faster than MsysGit (WSL is ~1s on my laptops). It is possibly slightly faster on 1903 as my laptop running it is faster than the other for this bench, despite having an older processor.
Now in a Linux VM it's approx 10 times faster than even WSL. And that should probably be even faster natively.
So anyway WSL is really usable and if you really only started 10 processes per sec something is wrong. Maybe you are using a crappy antivirus (I've heard that Kaspersky makes WSL extremely slow)
Well, I hadn't installed any antiviruses myself. I think Windows Defender was running, though. It's possible that my computer came with additional crapware on it.
Found my previous comment on it (which has a test case but not numbers): https://news.ycombinator.com/item?id=18226921